Synthesis and Characterization of Two [2]Catenanes Based on Phenylene-diacetylene Crown Ethers

Two charged donor-acceptor [2]catenanes were synthesized by the cyclization of the π-acceptor 1,1'-[1,4-phenylenebis-(methylene)]bis(4,4'-bipyridinium)bis(hexafluorophosphate)(2) and bis(bromomethyl)benzene with the templates of the π-donor phenylene-diacetylene crown ethers 1a and 1b in the yields of 31%, 35%, respectively. The mass spectra, ¹H and ¹³C NMR spectra confirm that the phenylene-diacetylene crown ethers, with a nonaromatic π-system, successfully template the cyclization of CBPQT⁴⁺. The X-ray crystallography analysis shows that the CBPQT⁴⁺ ring encircles around the phenylene motif of the crown ethers, leaving the 1,3-butadiyne fragment out of the cavity of CBPQT⁴⁺ ring. The mechanically interlocked structure of [2]catenanes was stabilized by the cooperative effects of π-stacking and hydrogen bonding interactions.